1. Field of the Invention
The present invention relates generally to a system for locating a mobile terminal, and more particularly to a system and method for locating a mobile terminal using SUPL (Secure User Plane Location) in a wireless communications network.
2. Description of the Related Art
In recent times, there has been an increased need for services that can provide the location information of a mobile communication set. Accordingly, it has become necessary to standardize the method of locating the mobile set using an IP (internet protocol) network by a reliable organization such as the OMA (Open Mobile Alliance Standardization).
One method of locating the mobile set that is particularly common at present is to provide auxiliary information (as of A-GPS: Assistant-Global Positioning System) for the mobile set or terminal and the positioning server. Among the various systems using such a positioning method, there has been proposed a method for locating the mobile set using the SUPL protocol.
The method for locating the mobile set using SUPL protocol provides the location information of a mobile set targeted by an SUPL agent according to a request of the SUPL agent. In this case, the SUPL location platform (SLP) reports to the service subscriber the location of the mobile set according to the change-area-type if the mobile set is positioned in the target area requested by the subscriber.
The conventional request services for locating the mobile set using SUPL are generally divided into immediate, deferred and periodic request services. The immediate request service (hereinafter immediate service) provides the location information once for a single request of the subscriber. Hence, if the subscriber requires to receive the location information of the mobile set several times, he must make multiple requests to the positioning server.
Thus, a repeated request service system has been developed as the periodic request service (hereinafter periodic service), to repeatedly provide the location information for the subscriber. The repeated request service system enables the positioning server to provide the location information repeatedly according to the criteria including duration of the service, start time, and stop time. For example, the repeated request service provides the location information calculated when the mobile set enters, leaves, or stays in the area designated by the subscriber.
In order to provide the periodic service, the mobile set and positioning server exchange the capacities of positioning methods with each other so as to select a positioning method proper for both. Meanwhile, the capacity of the positioning method does not change through the services, and therefore it can be transferred once to the positioning server. Nevertheless, the conventional method causes the mobile set and positioning server to continuously exchange the capacities of the positioning methods with each other whenever the location of the mobile set is calculated. Hence, the conventional method unnecessarily repeats the transmission of the data for the capacity of the positioning method, thereby resulting in unnecessary time consumption and an inefficient rate of radio data between the mobile set and the positioning server.